Radio receiving device

ABSTRACT

The influence of a multipath noise and an adjacent interference noise on the quality of reception of a broadcast is indexed in accordance with a received electric field strength level, and a broadcast station which is a station selection target is searched for using this index value.

TECHNICAL FIELD

The present invention relates to a radio receiving device having afunction of searching for a receivable broadcast station.

BACKGROUND ART

In a vehicle-mounted radio receiving device, the received electric fieldstrength varies as the vehicle moves. When the received electric fieldstrength of a broadcasting signal is at a strong electric field level, ahigh-quality radio sound can be outputted because the S/N ratio is good.In contrast, when the received electric field strength is at a weakelectric field level, the noise component quantities of a multipathnoise and an adjacent interference noise in the broadcasting signal havelarger variations than those in the case of an intermediate electricfield level or a strong electric field level.

Conventional radio receiving devices include a radio receiving devicethat makes a broadcast station search in consideration of variations inthe noise component quantities of a multipath noise and an adjacentinterference noise which correspond to the received electric fieldstrength level of a broadcasting signal. For example, in a broadcastingreceiver described in Patent Literature 1, a multipath noise and anadjacent interference noise which are detected from a broadcastingsignal are converted into DC voltages, and a summed DC voltage which isthe sum of these DC voltage values is used as a trigger signal for asearch start. When the received electric field strength of a broadcastis at a weak electric field level, it is determined that the receptionstate gets worse when the average of the summed DC voltage becomes equalto or greater than a threshold, and a search for a broadcast station isstarted.

CITATION LIST Patent Literature

Patent Literature 1: Japanese Unexamined Patent Application PublicationNo. 2001-60849

SUMMARY OF INVENTION Technical Problem

However, the influence of a multipath noise and an adjacent interferencenoise on the quality of reception of a broadcasting signal differsdependently on the received electric field strength level of thebroadcasting signal. Therefore, there is a problem is that because inthe value which is the result of simply adding the noise componentquantity of a multipath noise and the noise component quantity of anadjacent interference noise, the influence depending on the receivedelectric field strength level is not taken into consideration, abroadcast station which is a station selection target cannot becorrectly searched for.

The present invention is made in order to solve the above-mentionedproblem, and it is therefore an object of the present invention toprovide a radio receiving device that can properly search for abroadcast station which is a station selection target.

Solution to Problem

A radio receiving device according to the present invention includes anelectric field level determining unit, a point providing unit, an indexcalculating unit, and a determining unit. The electric field leveldetermining unit determines a received electric field strength level ofa broadcast. The point providing unit provides a multipath noise and anadjacent interference noise which are detected from a broadcastingsignal with point values corresponding to respective noise componentquantity ranges of the multipath and adjacent interference noises. Theindex calculating unit has arithmetic expressions in each of whichinfluence of a multipath noise and an adjacent interference noise onquality of reception of a broadcast is indexed, for respective receivedelectric field strength levels, selects an arithmetic expressioncorresponding to the received electric field strength level determinedby the electric field level determining unit from among the arithmeticexpressions, and calculates an index value by substituting the pointvalues provided by the point providing unit into the selected arithmeticexpression. The determining unit, when the index value calculated by theindex calculating unit is less than a threshold, determines that abroadcast station for which the index value is acquired is a stationselection target, whereas the determining unit, when the index value isequal to or greater than the threshold, excludes a broadcast station forwhich the index value is acquired from station selection targets.

Advantageous Effects of Invention

According to the present invention, the influence of a multipath noiseand an adjacent interference noise on the quality of reception of abroadcast is indexed in accordance with a received electric fieldstrength level, and a broadcast station which is a station selectiontarget is searched for using this index value. As a result, because theinfluence of a multipath noise and an adjacent interference noise on thequality of reception of a broadcast is determined in accordance with areceived electric field strength level, a broadcast station which is astation selection target can be properly searched for.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a block diagram showing the configuration of a radio receivingdevice according to Embodiment 1 of the present invention;

FIG. 2 is a block diagram showing the configuration of a control unit inEmbodiment 1;

FIG. 3 is a diagram showing a relation between noise component quantityranges of a multipath noise and an adjacent interference noise, and apoint value set to each of the noise component quantity ranges;

FIG. 4 is a diagram showing a relation between ranges of receivedelectric field strength levels and parameter values set to each of theranges;

FIG. 5 is a flowchart showing the operation of the control unit inEmbodiment 1;

FIG. 6 is a block diagram showing the configuration of a control unit inEmbodiment 2 of the present invention; and

FIG. 7 is a flowchart showing the operation of the control unit inEmbodiment 2.

DESCRIPTION OF EMBODIMENTS

Hereafter, in order to explain this invention in greater detail,embodiments of the present invention will be described with reference tothe accompanying drawings.

Embodiment 1

FIG. 1 is a block diagram showing the configuration of a radio receivingdevice 1 according to Embodiment 1 of the present invention, and showsthe hardware configuration of the radio receiving device 1. FIG. 2 is ablock diagram showing the configuration of a control unit 5, and showsthe functional configuration of the control unit 5. FIG. 3 is a diagramshowing a relation between noise component quantity ranges of amultipath noise and an adjacent interference noise, and a point valueset to each of the noise component quantity ranges. Further, FIG. 4 is adiagram showing a relation between ranges of received electric fieldstrength levels, and parameter values set to each of the ranges.

The radio receiving device 1 is implemented by car audio equipmenthaving a radio function, or the like, and has, for example, a seekfunction or a station listing function.

The seek function is to start a search for a broadcast station inresponse to a specific operation, and, when a receivable broadcaststation is found, automatically select this broadcast station. Thestation listing function is to search for a receivable broadcast stationand present a station list which is a list of broadcast stations foundin the search to a user. In either of the functions, a broadcast stationwhich is a station selection target is searched for.

The radio receiving device 1 includes an antenna 2, a radio unit 3, aDigital Signal Processor (DSP) 4, the control unit 5, and a memory 6, asshown in FIG. 1.

An RF signal (high frequency signal) which is a broadcasting signalreceived by the antenna 2 is inputted to the radio unit 3. The radiounit 3 is implemented by a digital radio tuner or an analog radiocircuit, and extracts, from the RF signal received by the antenna 2, theRF signal of a broadcast station which is requested to select, andperforms frequency conversion of the extracted RF signal into an IFsignal (intermediate frequency signal). The DSP 4 performs demodulationprocessing and sound processing on the basis of the IF signal, therebygenerating a sound signal. This sound signal is outputted as a soundfrom a speaker 7.

The control unit 5 performs a process of making a request of the radiounit 3 for selection of a station, a process of checking the quality ofreception of a broadcast, a process of determining a station selectiontarget in the seek function and in the station listing function, and amute process in the seek function, on the basis of reception stateinformation inputted from the DSP 4. In the reception state information,the received electric field strength, a multipath noise level, anadjacent interference level, and an IF level of the broadcasting signalare included.

It is shown that the higher the multipath noise level, the larger thenoise component quantity of the multipath noise included in thebroadcasting signal, and the higher the adjacent interference level, thelarger the noise component quantity of the adjacent interference noiseincluded in the broadcasting signal. Further, it is shown that thehigher the IF level, the larger the deviation of the frequency of theactually received broadcast station from the frequency which isrequested to be selected.

Further, the control unit 5 can be implemented by a Central ProcessingUnit (CPU) or the like. A CPU can function as the control unit 5 byperforming processing in accordance with a program stored in the memory6. The station list, data included in the broadcasting signal, and so onare displayed on the screen of the monitor 8 by the control unit 5.

The control unit 5 includes, as its functional configuration, anelectric field level determining unit 5 a, a point providing unit 5 b,an index calculating unit 5 c, a determining unit 5 d, and a stationselection control unit 5 e, as shown in FIG. 2.

The electric field level determining unit 5 a determines the receivedelectric field strength level of a broadcast. Concretely, the electricfield level determining unit 5 a determines whether the receivedelectric field strength level of a broadcast is a weak electric fieldlevel, an intermediate electric field level, or a strong electric fieldlevel, on the basis of the received electric field strength included inthe reception state information. For example, a weak electric fieldlevel falls within a level range lower than 30 dBμV, an intermediateelectric field level falls within a level range equal to or higher than30 dBμV and lower than 70 dBμV, and a strong electric field level fallswithin a level range equal to or higher than 70 dBμV.

The point providing unit 5 b provides a multipath noise and an adjacentinterference noise which are detected from the broadcasting signal withpoint values corresponding to their respective noise component quantityranges.

A point value is set for each of the noise component quantity ranges ofa multipath noise and an adjacent interference noise, as shown in FIG.3, and typifies the noise component quantities included in each of thenoise component quantity ranges. For example, even though the noisecomponent quantity of a multipath noise varies within a noise componentquantity range, the noise component quantity of the multipath noise ishandled using the point value set to this noise component quantityrange. As a result, because a variation in the noise component quantityis absorbed, it is possible to make an accurate search for a broadcaststation which is a selection target.

Further, although in the example of FIG. 3, the case in which the pointvalue set to each of the noise component quantity ranges for a multipathnoise is the same as that set to the corresponding one of the noisecomponent quantity ranges for an adjacent interference noise is shown,mutually different point values can be set. For example, when the degreeof influence of a multipath noise is determined to be higher than thatof an adjacent interference noise, the point value set to each of thenoise component quantity ranges for a multipath noise can be set to behigher than that set to the corresponding one of the noise componentquantity ranges for an adjacent interference noise.

The index calculating unit 5 c calculates an index value by substitutingthe point values provided by the point providing unit 5 b into anarithmetic expression by which the influence of a multipath noise and anadjacent interference noise on the quality of reception of a broadcastis indexed. Further, in order to index the influence of these noises onthe quality of reception of a broadcast for each received electric fieldstrength level, arithmetic expressions set for respective receivedelectric field strength levels are set to the index calculating unit 5 cin advance. The index calculating unit 5 c selects an arithmeticexpression corresponding to the received electric field strength leveldetermined by the electric field level determining unit 5 a from amongthese arithmetic expressions, thereby calculating an index value.

In the case of a weak electric field level, the influence of a multipathnoise and an adjacent interference noise on the quality of reception ofa broadcast is great. Therefore, in the index calculating unit 5 c, inorder to make the corresponding index value larger, for example, anarithmetic expression to add or multiply the point value for a multipathnoise and the point value for an adjacent interference noise is set asshown in the following equation (1) or (2). In this equation, d is theindex value, b is the point value set to the noise component quantityrange of a multipath noise, and c is the point value set to the noisecomponent quantity range of an adjacent interference noise.

d=b+c  (1)

d=b×c  (2)

In contrast, in the case of a range from an intermediate electric fieldlevel to a strong electric field level, the influence exerted by noisesis less than that in the case of a weak electric field level. Morespecifically, while in the case of a weak electric field level, thereare many noises in terms of audibility, in the case of a range from anintermediate electric field level to a strong electric field level, thesound may be heard clearly in terms of audibility. Therefore, in theindex calculating unit 5 c, in order to make the corresponding indexvalue smaller, for example, the following equation (3) or (4) is set asan arithmetic expression.

In this equation, d is the index value, b is the point value set to thenoise component quantity range of a multipath noise, and c is the pointvalue set to the noise component quantity range of an adjacentinterference noise. Parameters f and g have values set for each receivedelectric field strength level range, as shown in FIG. 4.

d=(b+c)−f  (3)

d=(b+c)/g  (4)

When the index value calculated by the index calculating unit 5 c isless than a threshold, the determining unit 5 d determines that abroadcast station for which this index value is acquired is a stationselection target, whereas when the index value is equal to or greaterthan the threshold, the determining unit excludes a broadcast stationfor which this index value is acquired from station selection targets.

For example, in a case in which the received electric field strengthlevel of a broadcast from a broadcast station found in the search is aweak electric field level, the point value b of a multipath noise is 3,and the point value c of an adjacent interference noise is 4, the indexvalue d=7 is calculated when the index calculating unit 5 c selects theabove-mentioned equation (1) as the arithmetic expression.

Because d≥E when a reference value E for determination which is theabove-mentioned threshold is 6, the determining unit 5 d excludes thisbroadcast station from station selection targets.

In contrast, when the received electric field strength level of abroadcast from a broadcast station selected the next time is equal to orgreater than 40 dBμV and less than 49 dBμV, the index calculating unit 5c selects the above-mentioned equation (3) or (4) because the receivedelectric field strength level is an intermediate electric field level.In this case, b=3 and c=4, and f=2 and g=1.2 shown in FIG. 4 aresubstituted into the above-mentioned equation, the index value d=5 ord=5.83 is calculated. Because either of the index values d is less thanE=6, the determining unit 5 d determines that this broadcast station isa station selection target. As a result, it is possible to make abroadcast station search in consideration of the influence of amultipath noise and an adjacent interference noise, the influence beingdependent on the received electric field strength level of a broadcast.

The station selection control unit 5 e controls the radio unit 3 in sucha way that a broadcast station which is determined to be a stationselection target by the determining unit 5 d is selected. For example,in the seek function, the station selection control unit 5 e controlsthe radio unit 3 to automatically select a broadcast station found inthe previous search from among broadcast stations which are determinedto be station selection targets by the determining unit 5 d. In thestation listing function, the station selection control unit 5 egenerates a station list of broadcast stations which are determined tobe station selection targets by the determining unit 5 d, and causes themonitor 8 to display the station list. In a case in which the radioreceiving device 1 has a sub-antenna and a sub-radio unit, in additionto the antenna 2 and the radio unit 3, a search made by the sub-radiounit in the background of the receiving operation of the radio unit 3 isalso included in the search in Embodiment 1.

Next, operations will be explained.

FIG. 5 is a flowchart showing the operation of the control unit 5, andshows a series of processes in the seek function or the station listingfunction.

First, the station selection control unit 5 e causes the radio unit 3 tomake a search for all receivable broadcast stations by controlling theradio unit 3 (step ST1). Here, the DSP 4 generates reception stateinformation about a broadcast station selected by the radio unit 3, andthe determining unit 5 d determines a receivable broadcast station onthe basis of a result of comparing the received electric field strengthincluded in this reception state information with a threshold. As aresult, all broadcast stations each having a received electric fieldstrength level equal to or greater than a weak electric field level aresearched for.

The electric field level determining unit 5 a determines whether thereceived electric field strength level of a broadcast is a weak electricfield level, an intermediate electric field level, or a strong electricfield level on the basis of the received electric field strengthincluded in the above-mentioned reception state information (step ST2).Next, on the basis of the multipath noise level and the adjacentinterference level which are included in the reception stateinformation, the point providing unit 5 b provides the multipath noiseand the adjacent interference noise with point values corresponding totheir respective noise component quantity ranges.

Next, the index calculating unit 5 c selects an arithmetic expressioncorresponding to the received electric field strength level determinedby the electric field level determining unit 5 a from among thearithmetic expressions preset for respective received electric fieldstrength levels.

The index calculating unit 5 c then calculates an index value bysubstituting the point values provided by the point providing unit 5 binto the arithmetic expression selected in this way (step ST3).

The determining unit 5 d determines whether or not the index valuecalculated by the index calculating unit 5 c is equal to or greater thanthe reference value for determination (step ST4).

When the index value is less than the threshold (NO in step ST4), thedetermining unit 5 d determines that a broadcast station for which thisindex value is acquired is a station selection target, and theprocessing shifts to a process of step ST6.

When the index value is equal to or greater than the threshold (YES instep ST4), the determining unit 5 d determines that a broadcast stationfor which this index value is acquired is an NG station and excludes thebroadcast station from station selection targets (step ST5).

When the seek function is performed (seek in step ST6), the stationselection control unit 5 e automatically selects a broadcast stationfound in the previous search from among broadcast stations which aredetermined to be station selection targets by determining unit 5 d (stepST7).

In contrast, when the station listing function is performed (stationlist in step ST6), the station selection control unit 5 e stores thebroadcast stations determined to be station selection targets in thememory 6 (step ST8).

Next, the station selection control unit 5 e checks whether or not thenext station returns to the broadcast station from which the searchrequest has been started (step ST9). The series of processes mentionedabove is performed by selecting all the broadcast stations found in thesearch in step ST1 one by one in descending order or ascending order oftheir reception frequencies. Therefore, the fact that the next stationreturns to the broadcast station from which the search request has beenstarted shows that the above-mentioned processes have been performed onall the broadcast stations.

Then, when the next station returns to the broadcast station from whichthe search request has been started (YES in step ST9), the stationselection control unit 5 e reads the broadcast stations which arestation selection targets from the memory 6, thereby generates a stationlist, and causes the monitor 8 to display the list (step ST10). Afterthat, the processing is ended.

In contrast, when the next station does not return to the broadcaststation from which the search request has been started (NO in step ST9),the electric field level determining unit 5 a selects the next station(step ST11) and the processing returns to the process of step ST2.

As mentioned above, the radio receiving device 1 according to Embodiment1 indexes the influence of a multipath noise and an adjacentinterference noise on the quality of reception of a broadcast inaccordance with a received electric field strength level, and searchesfor a broadcast station which is a station selection target by usingthis index value. By doing in this way, the influence of a multipathnoise and an adjacent interference noise on the quality of reception ofa broadcast is determined in accordance with the received electric fieldstrength level, and thus a broadcast station which is a stationselection target can be properly searched for. Embodiment 2.

FIG. 6 is a block diagram showing the configuration of a control unit 5Ain Embodiment 2 of the present invention.

The control unit 5A includes, as its functional configuration, anelectric field level determining unit 5 a, a point providing unit 5 b,an index calculating unit 5 c, a determining unit 5 d, a stationselection control unit 5 e, and an averaging unit 5 f. Here, because theelectric field level determining unit 5 a, the index calculating unit 5c, and the determining unit 5 d operate like the same components shownin FIG. 2, an explanation of their operations will be omitted.

The averaging unit 5 f calculates an average of noise componentquantities of a plurality of multipath noises and an average of noisecomponent quantities of a plurality of adjacent interference noises, themultipath and adjacent interference noises being detected from abroadcasting signal. The point providing unit 5 b provides a point valuecorresponding to a noise component quantity range in which each of theaverages of the noise component quantities is included.

Further, when there is a broadcast station having a weak electric fieldlevel, the station selection control unit 5 e controls a radio unit 3 tocause the radio unit to detect a plurality of multipath noises and aplurality of adjacent interference noises from a broadcasting signal ofthis broadcast station.

Next, operations will be explained.

FIG. 7 is a flowchart showing the operation of the control unit 5A, andshows a series of processes in a seek function or a station listingfunction. A process of step ST1 a of FIG. 7 is the same as that of stepST1 of FIG. 5.

On the basis of the received electric field strengths included inreception state information inputted from a DSP 4, the electric fieldlevel determining unit 5 a determines, out of broadcast stations foundin the search in step ST1 a, a broadcast station whose broadcast has areceived electric field strength level falling within a range from aweak electric field level to an intermediate electric field level (stepST2 a). At this time, when the received electric field strength level ofthe broadcast is a strong electric field level (NO in step ST2 a), theprocess of step ST2 a is repeated.

Alternatively, when the received electric field strength level of thebroadcast is a strong electric field level, the processing can shift toprocesses from step ST3 of FIG. 5.

When the received electric field strength level of the broadcast fallswithin the range from a weak electric field level to an intermediateelectric field level (YES in step ST2 a), it is determined that avariation in noise component quantities of multipath noises and avariation in noise component quantities of adjacent interference noisesare large. Therefore, the station selection control unit 5 e causes theradio unit 3 to detect a multipath noise and an adjacent interferencenoise m times at time intervals of n milliseconds from the broadcastingsignal of this broadcast station again by controlling the radio unit 3.The multipath noise level and adjacent interference level which aredetected at each time are outputted, as reception state information,from the DSP 4 to the averaging unit 5 f.

The averaging unit 5 f calculates an average A_(MPI) of the noisecomponent quantities of multipath noises and an average A_(ASI) of thenoise component quantities of adjacent interference noises in accordancewith the following equations (5) and (6), respectively (step ST3 a).N_(M)m is the noise component quantity of a multipath noise, and N_(A)mis the noise component quantity of an adjacent interference noise.

A _(MPI)=(N _(M)1+N _(M)2+N _(M)3+ . . . +N _(M) m)/m  (5)

A _(ASI)=(N _(A)1+N _(A)2+N _(A)3+ . . . +N _(A) m)/m  (6)

The point providing unit 5 b provides a point value corresponding to anoise component quantity range in which each of the averages A_(MPI) andA_(ASI) calculated by the averaging unit 5 f is included (step ST4 a).

For example, in the case of using a relation of FIG. 3 between noisecomponent quantity ranges and point values, a point value b=3 isprovided when the average A_(MPI) is 2.5. Further, when the averageA_(ASI) is 0.5, a point value c=1 is provided.

Because processes of steps ST5 a to ST12 a are the same as those ofsteps ST4 to ST11 of FIG. 5, an explanation of the steps will beomitted.

Further, although in the above-mentioned explanation, the averages ofnoise component quantities are calculated when the received electricfield strength level falls within the range from a weak electric fieldlevel to an intermediate electric field level, this embodiment is notlimited to this example.

For example, in step ST3 a, only when the received electric fieldstrength level is a weak electric field level, the averages of noisecomponent quantities can be calculated, or also when the receivedelectric field strength level is a strong electric field level, theaverages of noise component quantities can be calculated.

As mentioned above, the control unit 5A in Embodiment 2 includes theaveraging unit 5 f that calculates an average of noise componentquantities of a plurality of multipath noises and an average of noisecomponent qualities a plurality of adjacent interference noises, themultipath and adjacent interference noises being detected from abroadcasting signal. The point providing unit 5 b provides a point valuecorresponding to a noise component quantity range in which each of theaverages the noise component quantities is included.

By configuring in this way, even though a variation in noise componentquantities of multipath noises and a variation in noise componentquantities of adjacent interference noises are large, the influence ofthe variations is reduced, and thus a broadcast station which is astation selection target can be properly searched for.

It is to be understood that any combination of two or more of theabove-mentioned embodiments can be made, various changes can be made inany component according to the above-mentioned embodiments, and anycomponent according to the above-mentioned embodiments can be omittedwithin the scope of the invention.

INDUSTRIAL APPLICABILITY

Because the radio receiving device according to the present inventioncan properly search for a broadcast station which is a candidate forstation selection, the radio receiving device is suitable for, forexample, a vehicle-mounted radio receiving device in which the receivingenvironment of a broadcast varies as the vehicle moves.

REFERENCE SIGNS LIST

1 radio receiving device, 2 antenna, 3 radio unit, 4 DSP, 5, 5A controlunit, 5 a electric field level determining unit, 5 b point providingunit, 5 c index calculating unit, 5 d determining unit, 5 e stationselection control unit, 5 f averaging unit, 6 memory, 7 speaker, and 8monitor.

1. A radio receiving device comprising: a processor to execute a program; and a memory to store the program which, when executed by the processor, performs processes of, determining a received electric field strength level of a broadcast; providing a multipath noise and an adjacent interference noise which are detected from a broadcasting signal with point values corresponding to respective noise component quantity ranges of the multipath and adjacent interference noises; having arithmetic expressions in each of which influence of a multipath noise and an adjacent interference noise on quality of reception of a broadcast is indexed, for respective received electric field strength levels, selecting an arithmetic expression corresponding to the received electric field strength level determined from among the arithmetic expressions, and calculating an index value by substituting the point values provided into the selected arithmetic expression; and when the index value calculated is less than a threshold, determining that a broadcast station for which the index value is acquired is a station selection target, and when the index value is equal to or greater than the threshold, excluding a broadcast station for which the index value is acquired from station selection targets.
 2. The radio receiving device according to claim 1, the processes further comprising calculating an average of noise component quantities of a plurality of multipath noises and an average of noise component quantities of a plurality of adjacent interference noises, the multipath and adjacent interference noises being detected from the broadcasting signal, and providing point values corresponding to noise component quantity ranges in which the respective averages of the noise component quantities calculated are included. 